The invention relates to a process for the production of a tablet containing S-ibuprofen which rapidly releases the active compound.
S-Ibuprofen is the pharmacologically active enantiomer of the ibuprofen racemate. Ibuprofen is a generally known non-steroidal substance having analgesic, antiinflammatory and antipyretic action. It has been shown that the administration only of the S form instead of the racemate represents a significant therapeutic advantage. This is described e.g. in the documents EP-OS 0 267 321 or WO 89/00421.
S-Ibuprofen differs, however, significantly in its physical properties from the racemate, so that substantial difficulties occur in the preparation of solid oral forms when using conventional techniques. The melting point of S-ibuprofen is very low at 52.degree. C., while the racemate melts at 75.degree.-78.degree. C. This makes the use of conventional granulation techniques in the production of granules almost impossible, since owing to the addition of heat which is necessary during drying the active compound starts to melt or sinters. It is known from the literature that ibuprofen which is melted or sintered during processing shows an impaired in vivo bioavailability.
The melting point is a problem even in the production of film-coated tablets containing the highermelting ibuprofen racemate. Thus it is known that the bioavailability is likewise impaired in film-coated tablets which have been coated under excessively hot conditions.
Various administration forms have been described hitherto in the prior art. For example WO 88/02625 describes the production of a soft gelatin capsule which is filled with dissolved ibuprofen. In this case ibuprofen is dissolved in polyethylene glycol. The solubility therein can be further improved by neutralizing ibuprofen partially with alkali solutions, such as potassium hydroxide. This type of administration, however, is not suitable for S-ibuprofen, since either undesirably high decreases in content generally occur as a result of esterification reactions of S-ibuprofen with alcohols in this type of solution of the active compound, or else--which is more serious--racemization of the S-ibuprofen occurs as a result of the addition of potassium hydroxide.
EP-OS 0 299 668 describes the production of hard gelatin capsules by filling with melts. Capsules prepared in this way, however, only dissolve very slowly again, so that this principle is suitable rather for the production of sustained-release forms than of rapid-releasing forms. Melt-embedded materials also count as problematical inasmuch as during storage crystal modifications having altered bioavailability frequently occur.
The conventional matrix tablets claimed in U.S. Pat. No. 5,009,895 are likewise sustained-release formulations which, depending on the mixing ratio of S-ibuprofen to hydroxypropylmethylcellulose employed, lead to tablets whose release is delayed to a highly differing extent.
From the production engineering point of view, the conventional direct tabletting process has the disadvantages that the powder mixture to be compressed flows poorly, the dosing accuracy is inadequate, the tabletting speed is not sufficiently rapid and capping of these tablets cannot be avoided, which in turn makes coating difficult.